30-database-postgres

A set of rules for storing structured application data in PostgreSQL, a relational database. It covers database tables, schema changes, queries, and data-access code.

In plain words
What is it for?
Designing tables, writing migrations, adding indexes and relationships, isolating organizations in shared applications, and implementing repository-based database access.
Why use it?
It keeps data changes traceable and queries safer, while reducing problems such as missing constraints, slow lookups, and repeated database requests.

Cursor rule

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add rules/aiagentwithdhruv/ai-dev-stack/30-database-postgres
Clone the repo
git clone --depth 1 https://github.com/aiagentwithdhruv/ai-dev-stack
Per session 0 Nothing until a file matches its globs; then the whole rule loads.
When invoked 252 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00000 $0.00252
Opus 5 $0.00000 $0.00126
Sonnet 5 $0.00000 $0.00050
Haiku 4.5 $0.00000 $0.00025

Measured yesterday against content hash 90563edfc528, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

30-database-postgres scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured yesterday.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

rules/30-database-postgres.mdc · 34 lines

What it actually says

Database rules:

  • PostgreSQL is the source of truth for structured application data.
  • Use migrations for all schema changes.
  • Design tables with clear ownership, timestamps, and constraints.
  • Add indexes for common filters and joins.
  • Use foreign keys where appropriate.
  • Prefer soft-delete only when there is a real product need.

Schema design expectations:

  • Every core entity should have:
    • id
    • created_at
    • updated_at
  • For SaaS systems, include tenant/organization isolation where relevant.
  • Use enums or constrained fields for finite states where appropriate.
  • Keep schemas normalized unless denormalization is justified by performance needs.

Repository rules:

  • All DB access must go through repositories/data access layer.
  • Keep query code out of routes and services unless trivial and already patterned.
  • Parameterize queries.
  • Avoid N+1 query patterns.
  • Use transactions when multiple writes must succeed together.

Do not:

  • Write raw SQL inside controllers/routes.
  • Make schema changes without migration files.
  • Assume single-tenant if the product is multi-tenant.
Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. yesterday First seen · 34 lines · 0 tokens per session scan A 90563edfc528

Subscribe to this mod's changes

30-database-postgres is a cursor rule published in the GitHub repository aiagentwithdhruv/ai-dev-stack (10 stars, last pushed 2mo ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 252 tokens. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.